An integrated geophysical approach involving 2D modeling of electrical resistivity tomography (ERT) and magnetic methods has been employed at a highly heterogeneous site in Guangdong, South China, ...with a view at mapping the subsurface structures and delineating the weathered/fracture zones for groundwater potential. This study was carried out by ERT and magnetic surveys along the same profiles. One ERT survey was performed by the ABEM LUND Imaging System along four profiles each with a total of 81 electrodes, electrode spacing of 5 m and a spread length of 400 m. Another magnetic survey was conducted by two Geometrics G-856 proton precession magnetometers of 0.1 nT sensitivity along four profiles each with 79 magnetic measurements, a station interval of 5 m and a spread length of 390 m. The 2D modeling results of ERT and magnetic methods delineated several discontinuities (weathered/fracture zones) and three distinct layers i.e., top soil cover, weathered layer (weathered tuff) and unweathered layer (fresh bedrock). The integration of ERT and magnetic models shows good correlation with available upfront borehole information. The results suggest that groundwater is best accessible within the weathered/fracture zones in the study area. This integrated geophysical approach can be affectively used in weathered environment for groundwater exploration.
•An integrated geophysical approach to assess fractured zones for groundwater occurrence is proposed.•This approach was applied using 2D modeling of ERT and magnetic methods.•2D models of ERT and magnetic methods were obtained using RES2DINV and IX2D.•The integrated models revealed the groundwater reserves in the weathered/fracture zones.•This approach can be used to investigate the highly heterogeneous site for groundwater exploration.
Subsurface geological formation is essential to validate design assumptions for the construction of deep engineering structures, especially in the weathered terrains. The geological formation can be ...delineated using resistivity values through an electrical survey. However, the subsurface resistivity alone is ambiguous to interpret the subsurface geological units. As part of an ongoing investigation to select the key methods towards this end, an integrated geophysical survey through a combination of electrical resistivity tomography (ERT), induced polarization (IP), magnetic method and joint profile method (JPM) was carried out in a weathered terrain of South Huizhou, China. Resistivity, IP, and magnetic data were obtained using a variety of survey parameters. Subsurface resistivity was calibrated with upfront boreholes lithology to constrain geological formation into four discrete layers such as topsoil cover with resistivity 2–3257 Ωm, highly weathered layer having resistivity 2–636 Ωm, partly weathered layer with resistivity range 448–1204 Ωm, and unweathered bedrock having resistivity 791–116,497 Ωm. The integration of ERT with IP, magnetic and JPM delineated four faults namely F1, F2, F3 and F4, and several localized fractures. The weathered layer, fractures and faults were marked as the weakest zones for engineering projects, whereas the unweathered fresh bedrocks were identified as the most appropriate locations for the construction of deep structures in the study area. The weakest zones unsuitable for engineering structures were delineated as the most appropriate places of groundwater occurrence in the studied area revealed by low resistivity ranging from 2 to 1204 Ωm and overlapped by low chargeability less than 14.8 ms. This non-invasive geophysical approach suggests the most suitable locations highly significant not only for the future construction of engineering structures but also the exploitation of groundwater resources in the investigated area.
Geophysical methods are effectively used to delineate intrusion boundary between the fresh and saline aquifers because of their intrinsic capability to assess the lateral variations in the pore-water ...salinity. In this study, an integrated geophysical approach of vertical electrical sounding (VES) and electrical resistivity tomography (ERT) has been conducted to delineate the contaminated aquifers in the Lower Bari Doab, Pakistan. Electrical resistivity tomography (ERT) using Schlumberger array with 5 m electrode spacing was conducted along eleven profiles at three selected sites (LBD1, LBD2 and LBD3) in the investigated area. The surface geoelectrical method was performed by sixty electrical resistivity soundings using the same array with maximum current electrode spacing (AB = 150 m). The integration of formation resistivity with ten boreholes reveals four discrete subsurface layers i.e., clay having saline aquifer, clay-sand containing brackish aquifer, sand with fresh aquifer and gravel-sand containing fresh aquifer. Estimation of Dar-Zarrouk Parameters (i.e., longitudinal resistivity, transverse resistance and longitudinal conductance) from different combinations of aquifer thickness and resistivity delineated the fresh, brackish and saline water zones with specific values range through mapping and graphical analysis. Geochemical method was performed on forty wells for main cations (K+, Na+, Ca2+ and Mg2+), anions (SO42−, Cl−, HCO3– and NO3−) and other parameters (As, EC, TDS and pH) to validate the results obtained from the geophysical methods. The fresh/saline aquifers delineated by the inclusion of ERT and geoelectrical method are in good agreement with those revealed by the physicochemical analysis and the local hydrogeological data. The results suggest that the use of non-invasive geophysical methods can reduce the number of expensive boreholes to obtain an interface between the fresh and saline water for the exploitation of fresh groundwater resources in any large area of homogeneous or heterogeneous aquifers.
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•A geophysical approach of VES and ERT to delineate the fresh-saline interface in alluvial aquifers is proposed.•Calibration between resistivity and boreholes data constrained subsurface formation into a three layered model.•The fresh/saline aquifers evaluated by geophysical methods were validated by geochemical method.•Low-cost geophysical methods can efficiently reduce expensive boreholes to assess the fresh/saline aquifers.
An integrated study using geophysical method in combination with pumping tests and geochemical method was carried out to delineate groundwater potential zones in Mian Channu area of Pakistan. ...Vertical electrical soundings (VES) using Schlumberger configuration with maximum current electrode spacing (AB/2 = 200 m) were conducted at 50 stations and 10 pumping tests at borehole sites were performed in close proximity to 10 of the VES stations. The aim of this study is to establish a correlation between the hydraulic parameters obtained from geophysical method and pumping tests so that the aquifer potential can be estimated from the geoelectrical surface measurements where no pumping tests exist. The aquifer parameters, namely, transmissivity and hydraulic conductivity were estimated from Dar Zarrouyk parameters by interpreting the layer parameters such as true resistivities and thicknesses. Geoelectrical succession of five‐layer strata (i.e., topsoil, clay, clay sand, sand, and sand gravel) with sand as a dominant lithology was found in the study area. Physicochemical parameters interpreted by World Health Organization and Food and Agriculture Organization were well correlated with the aquifer parameters obtained by geoelectrical method and pumping tests. The aquifer potential zones identified by modeled resistivity, Dar Zarrouk parameters, pumped aquifer parameters, and physicochemical parameters reveal that sand and gravel sand with high values of transmissivity and hydraulic conductivity are highly promising water bearing layers in northwest of the study area. Strong correlation between estimated and pumped aquifer parameters suggest that, in case of sparse well data, geophysical technique is useful to estimate the hydraulic potential of the aquifer with varying lithology.
Article impact statement: An integrated geoelectrical method as a tool for the evaluation of groundwater potential in Mian Channu area of Pakistan.
Estimation of hydraulic parameters is important for the prediction of the future availability of groundwater reserves. Conventionally, pumping tests are conducted on boreholes to measure these ...parameters. However, such tests are costly and time consuming, and can only provide limited spatial information. An integrated approach of geophysical method and pumping tests is cost-effective and efficient alternative for the estimation of aquifer parameters. A geophysical method of vertical electrical sounding (VES) was carried out in Huizhou ADS site of China for the delineation of aquifer potential zones to assess the groundwater resources contained within the weathered rock. Initially, the pumping test data were used to determine the hydraulic parameters namely hydraulic conductivity (K
w
) and transmissivity (T
w
) for available production wells. Afterwards, one empirical relation between pumped hydraulic conductivity (K
w
) and aquifer resistivity (ρ
a
), and another between pumped transmissivity (T
w
) and transverse resistance (T
r
) were obtained to estimate hydraulic conductivity (K) and transmissivity (T) for all VES stations where pumping tests were not conducted. In this way, the entire study area was investigated to delineate the aquifer potential zones i.e., high potential aquifer zone with ρ
a
< 100 Ωm, T > 150 m
2
/day and K > 4 m/day, medium potential aquifer zone with ρ
a
ranging from 100 to 150 Ωm, T from 100 to 150 m
2
/day and K from 3 to 4 m/day, poor potential aquifer zone with ρ
a
from 150 to 300 Ωm, T from 50 to 100 m
2
/day and K from 2 to 3 m/day, and negligible potential aquifer zone with ρ
a
> 300 Ωm, T < 50 m
2
/day and K < 2 m/day. This investigation also deciphers functional analogous relation of Ω
a
with K and T
r
with T in Huizhou, China. Therefore, similar integrated approach can be used in any geological similar area where the aquifer properties are required for the management of groundwater reserves.
Angiopoietin-like protein 4 (ANGPTL4) has been associated with a variety of diseases. It is known as an endogenous inhibitor of lipoprotein lipase (LPL), and it modulates lipid deposition and energy ...homeostasis. ANGPTL4 is cleaved by unidentified protease(s), and the biological importance of this cleavage event is not fully understood with respect to its inhibitory effect on LPL activity. Here, we show that ANGPTL4 appears on the cell surface as the full-length form, where it can be released by heparin treatment in culture and in vivo. ANGPTL4 protein is then proteolytically cleaved into several forms by proprotein convertases (PCs). Several PCs, including furin, PC5/6, paired basic amino acid-cleaving enzyme 4, and PC7, are able to cleave human ANGPTL4 at a consensus site. PC-specific inhibitors block the processing of ANGPTL4. Blockage of ANGPTL4 cleavage reduces its inhibitory effects on LPL activity and decreases its ability to raise plasma triglyceride levels. In summary, the cleavage of ANGPTL4 by these PCs modulates its inhibitory effect on LPL activity.
In areas where weathering has hydrogeological significance, geophysical methods can assist to map the subsurface characteristics for groundwater occurrence. In this study, electrical resistivity ...tomography (ERT) survey in combination with joint profile method (JPM), magnetic method and borehole data was conducted to investigate the aquifer potential in strongly weathered volcanic rocks. The aim was to assess the geological units related to the water-bearing formation of aquifer systems in South Guangdong, China. The resistivities were measured along four profiles each with a total of 81 electrodes, a spread length of 400 m and an electrode spacing of 5 m insuring continuous coverage. The data from a borehole survey revealed three different layers i.e., highly weathered layer, partly weathered layer and fresh basement rock, whose respective thickness were integrated into ERT images to get more useful results about the real resistivity ranges of the these layers (i.e., 22 Ωm–345 Ωm for highly weathered layer, 324 Ωm–926 Ωm for partly weathered and 913 Ωm–2579 Ωm for fresh bedrock). The electrical resistivity imaging including the surface topography provides spatial variations in electrical properties of the weathered/unweathered layers since resistivity depends on the properties of a material rather than its thickness. ERT sections were integrated with JPM and magnetic method to delineate the main faults (F1, F2 and F3). ERT sections show a geometric relationship between different layered boundaries, particularly those of the aquifers with fresh basement and surface topographies. These layers comprise an overburden of 50 m thickness revealed by ERT sections. The results show that weathered and partly weathered layers between the topographic surface and bed rock yield maximum aquifer potential in the study area. ERT imaging method provides promising input to groundwater evaluation in the areas of weathered environment with complex geology.
The gene encoding the proprotein convertase subtilisin/kexin type 9 (PCSK9) is linked to familial hypercholesterolemia, as are those of the low‐density lipoprotein receptor (LDLR) and apolipoprotein ...B. PCSK9 enhances LDLR degradation, resulting in low‐density lipoprotein accumulation in plasma. To analyze the role of hepatic PCSK9, total and hepatocyte‐specific knockout mice were generated. They exhibit 42% and 27% less circulating cholesterol, respectively, showing that liver PCSK9 was responsible for two thirds of the phenotype. We also demonstrated that, in liver, PCSK9 is exclusively expressed in hepatocytes, representing the main source of circulating PCSK9. The data suggest that local but not circulating PCSK9 regulates cholesterol levels. Although transgenic mice overexpressing high levels of liver and circulating PCSK9 led to the almost complete disappearance of the hepatic LDLR, they did not recapitulate the plasma cholesterol levels observed in LDLR‐deficient mice. Single LDLR or double LDLR/PCSK9 knockout mice exhibited similar cholesterol profiles, indicating that PCSK9 regulates cholesterol homeostasis exclusively through the LDLR. Finally, the regenerating liver of PCSK9‐deficient mice exhibited necrotic lesions, which were prevented by a high‐cholesterol diet. However, lipid accumulation in hepatocytes of these mice was markedly reduced under both chow and high‐cholesterol diets, revealing that PCSK9 deficiency confers resistance to liver steatosis. Conclusion: Although PCSK9 is a target for controlling hypercholesterolemia, our data indicate that upon hepatic damage, patients lacking PCSK9 could be at risk. (HEPATOLOGY 2008;48:646–554.)
2D electrical resistivity tomography (ERT) coupled with electrical resistivity profiling, induced polarisation, and self-potential (ER-IP-SP) measurements and pumping-test data has been used to ...acquire subsurface electrical properties for the assessment of groundwater reserves in weathered terrains of Huidong County, China. In this investigation, ERT was performed using a pole-dipole array with 305 measurements, and ER-IP-SP with 127 stations, both along three profiles. A least-squares inversion technique is used for the post processing of the ERT data to generate 2D models of the subsurface geologic units. The following deductions are made based on the 2D ERT modelling. The average depth of fresh basement is generally 10-30 m. Three distinct layers were interpreted, i.e. 5-10 m thick topsoil cover with resistivity <1800 Ωm (above the water table), 5-25 m thick weathered layer with resistivity <900 Ωm (below the water table), and fresh bedrock with resistivity >900 Ωm (below the water table). These layers comprise the 50 m thick overburden revealed by the inverted sections. The ERT models were incorporated with ER-IP-SP to delineate various discontinuities. Groundwater resources enclosed in the weathered/fractured zones were estimated by hydraulic conductivity (K) and transmissivity (T) into three different aquifer zones with specific ranges of T and K (i.e. high, medium, and low yield aquifer). The results suggest that the best potential groundwater resources are contained within fractures/discontinuous zones. The results are well in line with the hydrogeological information available for the investigated area. This geophysical approach is useful to assess the groundwater potential where the weathering has hydrogeological significance.
A novel, real-time, homogeneous fluorogenic lipoprotein lipase (LPL) assay was developed using a commercially available substrate, the EnzChek lipase substrate, which is solubilized in Zwittergent. ...The triglyceride analog substrate does not fluoresce, owing to apposition of fluorescent and fluorescent quenching groups at the sn-1 and sn-2 positions, respectively, fluorescence becoming unquenched upon release of the sn-1 BODIPY FA derivative following hydrolysis. Increase in fluorescence intensity at 37°C was proportional to LPL concentration. The assay was more sensitive than a similar assay using 1,2-O-dilauryl-rac-glycero-3-glutaric acid-(6-methylresorufin ester) and was validated in biological samples, including determination of LPL-specific activity in postheparin mouse plasma. The simplicity and reproducibility of the assay make it ideal for in vitro, high-throughput screening for inhibitors and activators of LPL, thus expediting discovery of drugs of potential clinical value.
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